Electrical equipment is wired in many instances with a multiplicity of wires which have to be soldered or wrapped on a specific set of terminals. The terminals may be in a plug which has a series of predesignated connection points and which is, in turn, generally plugged into an analogous receptacle which receives the plug for making an electrical connection.
Oftentimes, wires are connected between two distant points on circuit boards or panels which have analogous designations to the points to which they have been previously wired. The ability to identify the particular designation of a wire which has to be connected at a location remote from the point to which it has been initially connected or wired is difficult. This has been particularly true when a large bundle of wires has been preconnected to a plurality of predesignated connection points and led in a bundle, harness or conduit to a distant location. When the bundle has been led to a distant location, it is virtually impossible to determine the predesignation of the wire and/or the predesignation of the point to which it is to be connected.
Such problems have led to the development of devices such as whose shown in U.S. Pat. Nos. 3,609,538 and 3,740,644 assigned to the assignee of the present invention. The '538 patent discloses a wire identification system in which a low voltage source is coupled to one end of a randomly selected conductor in a multiconductor cable, and the resulting signal developed in the selected conductor is decoded by a diode matrix coupled to the opposite ends of all of the conductors in said multiconductor cable to produce "tens" and "units" outputs which drive respective display indicators to visually designate the particular cable which has been randomly selected. The '644 patent is similar to the '538 patent, but has improvements in that the unit disclosed therein has the ability to operate in either a random mode or a select mode (wherein the display is inhibited until a particular wire is found) and also has the advantage of being able to use a portion of the user's body as a manipulative extension of a probe in such a way that the operator's finger completes a very low current conductive path from the power source through the probe and through the wire being touched.
Another type of prior art apparatus useful in identifying the wires of a multiconductor harness is similar to those described in the aforementioned '538 and '644 patents, but varies slightly in its circuit configuration by including means for sequentially energizing the outputs of a diode matrix. When the probe (such as the user's finger) is applied to an energized line, a gated signal is employed to stop a clock at the particular designation corresponding to the wire being touched, thereby creating a display of the conductor engaged by the operator's finger.
A problem analogous to the identification of wires of a multiconductor cable is the problem of testing a harness (either during or after assembly) to confirm that the conductors of the harness have been interconnected to the proper end points. One such technique prevalent in the industry for verifying the proper interconnections and integrity of an assembled harness (or for verifying the proper interconnection of the individual conductors as the harness is being assembled) is to employ a "known good" harness as a standard against which the assembled harness or harnesses may be compared to verify their accuracy. For example, the known good harness may be situated beneath a work surface upon which an assembler is preparing new harnesses. The respective end points of the good harness are electrically brought up into the area accessible by the worker. In assembling the new harness, one end of the wires thereof are electrically connected, for example through a plug, to one set of ends of the known good harness positioned beneath the work area. The harness assembler may then connect the opposite ends of the harness wires under assembly to electrical leads connected to the opposite ends of the good harness which is functioning as the standard. It will be appreciated that when the assembler correctly assembles the opposite ends of a given wire, a circuit will be completed through that wire and the corresponding wire in the known good harness which fact may then be used to energize a visual and/or audible signal indicating the proper termination, which signal is derived from the completed circuit. Of course, an incorrect termination by the assembler may be visually displayed as well.
It will be appreciated that the technique of continually comparing the harness under construction, or one which has been completed, to an actual known good harness which functions as a standard for comparison purposes is a rather complex, cumbersome technique. Among its many drawbacks is the fact that the plurality of "known good" harnesses must be initially constructed, one such known good harness must be provided in a special jig at each assembly station, and each jig must be specially constructed to facilitate the construction of a specified harness in that new known good harnesses and new jigs must be provided each time a different harness is to be assembled on the production line. Also, when a harness has been tested in the field or at a place remote from the location of the production line, either a known good harness must be shipped out to the remote location or the harness to be tested must be shipped to the location of the production line.
More recent attempts to facilitate the testing of completed harnesses have suggested the use of an apparatus having an internal memory to store information representative of the circuit connectors of a known good harness for comparison purposes with the conductors of the harness being examined. Such prior art devices have had drawbacks, however, in their inability to function in a monitor mode (i.e., useable during assembly of the harness to verify connections on a wire by wire basis); have been unable to verify multiple circuits (where a plurality of conductors are connected in common); have not employed transferable internal storage means (thereby making it difficult to interchange information between like devices); and/or have not had the capability of "learning" the known good harness by merely examining it (thereby requiring that information representative of the known good harness be physically inputed, for example by keypunching, into storage).